The present invention relates generally to the technology for measuring the levels or concentration of a gas in a monitored environment, and, more particularly, to a gas concentration measurement technique and system that is useful for remotely monitoring the concentration of a fire suppression agent such as HALON within military and commercial aircraft engine bays and cargo compartments.
The recent crash in Florida of a Valujet aircraft has stimulated discussion that might lead to FAA requirements for fire suppression equipment in commercial aircraft cargo holds. Presently, HALON is the primary fire suppression agent used in military and commercial aircraft. However, since halons are the worst known ozone-depleting chemicals (ODCs), alternative fire suppression agents are currently being sought.
In general, existing fire suppression systems include a fire suppression agent distribution system that distributes the fire suppression agent to the aircraft engine bays and selected cargo compartments. In a typical application, in order to effectively extinguish a fire, concentrations of fire suppression agent must be in excess of 6% for a period of 0.5 seconds. Lower concentrations or shorter time periods reduce effectiveness, and conversely, higher concentrations and/or longer time periods waste suppression. Additionally, oversizing the system can result in toxic concentrations with some fire suppression agents.
Typically, the fire suppression system undergoes a ground-based certification or qualification testing procedure in which the concentration of the fire suppression agent within the environments where the agent is distributed, i.e., within the aircraft engine bays and cargo compartments, is determined, in order to confirm proper operation of the fire suppression system. However, this procedure only certifies the proper operation of the fire suppression system prior to flight. None of these gas concentration measurement systems that are used in pre-flight certification testing of fire suppression systems are capable of being flown on the aircraft to monitor the concentration of the fire suppression agent during flight (e.g., during operation of the fire suppression system), in order to verify proper operation of the fire suppression system when it is activated and/or to provide feedback data that could enable the level of the fire suppression agent to be dynamically adjusted as required to ensure safe, effective, efficient, and reliable operation of the fire suppression system.
In this connection, the presently available gas concentration measurement systems that are used in pre-flight certification testing of fire suppression systems, such as the Pacific Scientific Halonizer, are generally undesirably complex, bulky, and expensive, and further, are either limited in the number of sample positions that can be monitored simultaneously, or are very slow, thereby limiting the accuracy or speed, respectively, of the gas concentration monitoring system, and thus, the safety, effectiveness and efficiency of the associated fire suppression system. For instance, the Pacific Scientific Halonizer, which was designed to monitor HALON concentrations for certification/qualification of aircraft fire suppression systems, has high data rates, but can only monitor four sample positions. Another device used by Pacific Scientific can multiplex twenty sample positions (via an electro-mechanical sampling system), but the sample rate for any one position is approximately only one sample every two seconds (i.e., 30 samples/minute).
Based on the above, it can be appreciated that there presently exists a need in the art for a fire suppression agent gas concentration monitoring system that overcomes the drawbacks and shortcomings of the presently available technology, and which is preferably capable of being flown on an aircraft. More particularly, there presently exists a need for a fire suppression agent gas concentration monitoring system that is fast and accurate, yet also small, low-cost, and reliable. Ideally, such a gas concentration monitoring system should have a large dynamic range and be implemented as a single, compact device. The present invention meets these objectives and fullfills this need in the art.